Organic 2 Review Problem 327

Organic 2 Review Problem 327 - dialkyl alkylphosphonate...

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PREPARATIONS 311 dropping-funnel by an inlet-tube (which carries a calcium chloride tube and which dips just below the surface of the reaction-mixture) and an outlet-tube. Draw dry air through the mixture for 45 minutes to remove as much hydrogen chloride as possible. Distil under reduced pressure and collect the fraction of b.p. 8i°/i5 mm. Yield, about 15 g- The unsubstituted hydrogen atom of the dialkyl hydrogen phosphites can be readily replaced by chlorine, and thence by many other substituents including fluorine. Diethyl Ethylphosphonate. C 2 H 5 PO(OC 2 Hg) 2 . When an alkyl halide is heated with a trialkyl phosphite, an ester of a phos- phonic acid is produced. This is known as the Arbusov Reaction: OR OR / / P-OR + R'Cl -> R'—P—OR + RCl \ Il OR O (I) If R = R', the reaction appears to be catalytic as a small quantity of R'Cl will suffice to convert a considerable quantity of the trialkyl phosphite into the
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Unformatted text preview: dialkyl alkylphosphonate (I). As little as o-i mol. of the alkyl iodide will suffice to isomerise the trialkyl phosphite. The Arbusov Reaction probably takes the following course. OR R' OR P-OR + R'Cl - P-OR \ /\ OR Cl OR R' OR OR P-OR -* R'POR + RQ . VY l! Cl O-L-R O In the reaction described below triethyl phosphite (p. 308) is heated with ethyl iodide to give diethyl ethylphosphonate. Although theoretically a very small amount of ethyl iodide would suffice, it is advantageous to use more than the minimum amount so as to reduce the temperature of the boiling reaction-mixture. Required: Triethyl phosphite, 16-9 g.; ethyl iodide, 10 g. Heat together under a good reflux water-condenser fitted with...
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